<?php

    /*
     * 生成随机字符串
     * @param int $length 生成随机字符串的长度
     * @param string $char 组成随机字符串的字符串
     * @return string $string 生成的随机字符串
     */
    function str_rand($length = 32, $char = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ') {
        if(!is_int($length) || $length < 0) {
            return false;
        }

        $string = '';
        for($i = $length; $i > 0; $i--) {
            $string .= $char[mt_rand(0, strlen($char) - 1)];
        }

        return $string;
    };
?>